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<h1><a href="https://archiveofourown.org/works/24042370">by the light of the moon</a> by <a class='authorlink' href='https://archiveofourown.org/users/youngjo/pseuds/youngjo'>youngjo</a></h1>

<table class="full">

<tr><td><b>Category:</b></td><td>ATEEZ (Band)</td></tr>

<tr><td><b>Genre:</b></td><td>Bioluminescence, Biting, Breeding, Established Relationship, Hand Jobs, Knotting, M/M, Marking, mermaid!au, unconventional anatomy &amp; dicks</td></tr>

<tr><td><b>Language:</b></td><td>English</td></tr>

<tr><td><b>Status:</b></td><td>Completed</td></tr>

<tr><td><b>Published:</b></td><td>2020-05-06</td></tr>

<tr><td><b>Updated:</b></td><td>2020-05-06</td></tr>

<tr><td><b>Packaged:</b></td><td>2021-05-02 16:14:58</td></tr>

<tr><td><b>Rating:</b></td><td>Explicit</td></tr>

<tr><td><b>Warnings:</b></td><td>No Archive Warnings Apply</td></tr>

<tr><td><b>Chapters:</b></td><td>1</td></tr>

<tr><td><b>Words:</b></td><td>3,407</td></tr>

<tr><td><b>Publisher:</b></td><td>archiveofourown.org</td></tr>

<tr><td><b>Story URL:</b></td><td>https://archiveofourown.org/works/24042370</td></tr>

<tr><td><b>Author URL:</b></td><td>https://archiveofourown.org/users/youngjo/pseuds/youngjo</td></tr>

<tr><td><b>Summary:</b></td><td><div class="userstuff">
              <p>Their people had passed down the tale for generations. The light meant death, and the moment you saw it, you were doomed. Yeosang wasn't sure what death felt like, but he knew he'd come back again.</p>
            </div></td></tr>

<tr><td><b>Relationships:</b></td><td>Choi San/Kang Yeosang</td></tr>

<tr><td><b>Comments:</b></td><td>19</td></tr>

<tr><td><b>Kudos:</b></td><td>228</td></tr>

<tr><td><b>Collections:</b></td><td>leviathanfest</td></tr>

</table>

<a name="section0001"><h2>by the light of the moon</h2></a>
<div class="story"><div class="fff_chapter_notes fff_head_notes"><b>Author's Note:</b><blockquote class="userstuff">
      <p>written for leviathan!</p><p>prompt #15 — bioluminescent creature of some kind</p><p>san is a dragonfish and yeosang is atlantean !</p>
    </blockquote></div><div class="userstuff module">
    
    <p>
  <span>“Don’t stay out too late, Yeosang. You know what will happen if you’re reported missing in the morning,” Seonghwa’s soft voice scolded.</span>
</p><p>
  <span>Yeosang groaned as he finished slipping an earring made from weathered shells into his ear. “Don’t worry, Seonghwa! Have I ever been late?”</span>
</p><p>
  <span>“No,” his advisor replied, sighing. </span>
</p><p>
  <span>Yeosang observed him in the milky reflectiveness of his vanity, crafted from the highest quality clam shell their little underwater world could get ahold of. Seonghwa was draped in pretty shells and beautiful pearls, strung together with carefully maintained seaweed. His body was humanoid but fins of the prettiest baby blue poked from his elbows, wrists, ears, and even his ankles and calves. His feet were more fin-shaped, elongated and webbed, perfect for swimming. Seonghwa was a blue betta fish, one of the last of his kind, and carried the graceful gentleness of all those who came before him. </span>
</p><p>
  <span>Yeosang mirrored him, though his fins were the color of the softest coral. Normally, he would be wearing more jewelry than Seonghwa, given his status as the Atlantean Prince. But for where he was going … he would not need it. </span>
</p><p>
  <span>“The sea is almost ink, Yeosang. Are you sure now is a good idea?”</span>
</p><p>
  <span>He slipped from his chair and propelled himself over to Seonghwa, placing a webbed hand on his shoulder. “You worry too much. I’ll be fine!” Yeosang smiled softly, for he knew what Seonghwa did not. </span>
</p><p>
  <span>“It’s my job to worry,” Seonghwa mumbled. “I’m your advisor, and I </span>
  <em>
    <span>advise</span>
  </em>
  <span> that you stay home.”</span>
</p><p>
  <span>“Your advice is noted.” Yeosang winked, dropping his head. He swam over to the window, throwing a glance over his shoulder. “I’ll be okay, Seonghwa, honest. He’ll never let anything bad happen to me.” The prince didn’t give him a chance to answer again. He slipped through the window, pushing his way through wavering kelp, and propelled himself to the ocean floor. Yeosang knew the patrols of the castle better than anyone. It took no effort at all to slip out, just as usual. </span>
</p><p>
  <span>The Atlantean wasn’t going without purpose though. He kicked his legs as he swam, the string of pearls around his throat rolling gently along his skin. Swimming around coral and seaweed, he drew closer and closer to his destination as the ocean began to turn ever darker around him.</span>
</p><p>
  <span>So, what</span>
  <em>
    <span> was</span>
  </em>
  <span> his destination?</span>
</p><p>
  <span>A place he had visited often following the last moon phase cycle. The home of a creature he had often heard about in fishtales and been told to avoid. Dangerous, cunning, terrifying—the creature was none of those things. No, he was simply lonely, cast out to the edges of their society and complacent in his realization that he would fade to nothing but a memory, until that too disappeared … until Yeosang came along.</span>
</p><p>
  <span>By the time he arrived, the ocean around him was pitch black. He moved on pure instinct, allowing the flow of the current and his memory to guide him. Yeosang only bumped into a rock once luckily before he sensed he was approaching his destination. Holding out his hands before him, they came into contact with a familiar stone. It was surprisingly warm under his fingers, indicating that it was, indeed, what he was looking for. Swimming further, he touched another, then another, until a faint glow began to appear in the distance. Soft and gentle, pulling him closer and lulling his mind into a cloudy haze the bigger it grew. Yeosang felt as if he were drifting rather than swimming, watching as the light separated into two focal points. </span>
</p><p>
  <span>They flickered as he approached, Yeosang raising his hands towards them. Just as he went to grasp one, it fluttered from his grip. He watched it dance out of reach before both lights vanished, leaving him in pure darkness. His heartbeat quickened as the faintest hint of fear stained his tongue. </span>
</p><p>
  <span>All at once, bright light blinded him.</span>
</p><p>
  <span>Yeosang blinked against it as his eyes fought to adjust before he could vaguely make out a shape. A beautifully intricate pattern of blue dots swayed side to side before him. They trailed down, spiraling along what one would assume was a tail. They all glowed with the same intensity of the original blue lights, those too hovering overhead. Then, finally, lights mirroring eyes flickered into view and Yeosang smiled. </span>
</p><p>
  <span>“You waited for me,” he whispered.</span>
</p><p>
  <span>The lights moved closer, a hand cupping his cheek with the gentlest touch he had ever felt. “I will always wait for you,” the creature replied.</span>
</p><p>
  <span>Yeosang leaned into the touch before swimming closer, pressing their bodies together. The being he had snuck out to meet was a black dragonfish, one of the sea’s cruelest, prettiest merfolk variations. He shared none of the qualities that had earned dragonfish their position in the sea, cast to the edges and persecuted for their existence. They were vastly different from an Atlantean of course but not in a bad way—at least in Yeosang’s eyes.</span>
</p><p>
  <span>His name was San, and he had been in love with him for more time than he could recall.</span>
</p><p>
  <span>“San, I missed you.” Hands slid around his waist, pulling him close. The dragonfish curled his tail around Yeosang’s left leg. He was larger, easily twice the size of Yeosang, and engulfed the whole of his body with little effort. No place else gave him as strong of comfort as San’s arms.</span>
</p><p>
  <span>“I missed you too.” San leaned down, nuzzling into his hair. The two orbs of light—San’s “feelers” as he had explained once—extended to gently run along his cheeks. “I was worried you’d gotten lost. It’s so dark for you Atlanteans out here.”</span>
</p><p>
  <span>“Never,” Yeosang murmured, running his hands down the spikes protruding from San’s spine. His fingertips hit scales, warm and smooth at the dragonfish’s waist. “The sea knows the way; it always guides me straight to you.”</span>
</p><p>
  <span>“I’m glad.” </span>
</p><p>
  <span>Yeosang felt his tail uncurl, and then San propelled them forward, most likely towards his den. It was a small underwater cave filled with plants that glowed with the same soft light as San’s body, and it was the only place he could truly see the face of the dragonfish he loved and adored. It didn’t take long to reach, a soft light growing more intense the closer they grew. No one dared invade San’s resting place. While he may have been gentle for such a dangerous creature, those in the sea refused to believe so. So they stayed away, but it had never bothered San much; he preferred being alone. Until Yeosang came along anyway.</span>
</p><p>
  <span>He cast his eyes to San’s face as they swam within the den. The lights from the weathered stone and carefully maintained plants illuminated his features. San had always been handsome, his face narrow and lips curved into a natural pout. Scales were spattered along his skin, mismatched and unsymmetrical. The marks containing his bioluminescence were, however. His entire body, from his cheeks down to the fins of his tail, were adorned in a matching pattern of glowing markings. He was breathtaking, truly, and would surely turn the heads of everyone who ever saw him.</span>
</p><p>
  <span>“Your heartbeat is a little quicker today; are you feeling alright?” San questioned, laying upon the soft grasses; his feelers ran reassuringly along Yeosang’s cheeks.</span>
</p><p>
  <span>“Yes … I’m just a little excited. I missed you.” Yeosang lifted his hand, running his fingers along the feelers checking him for signs of injury. “This is the first time I’ve been able to sneak out since you were spotted.”</span>
</p><p>
  <span>San hummed, the sound deep within his chest. It rumbled through Yeosang’s body in an almost therapeutic way. “I apologize. I should be more careful.”</span>
</p><p>
  <span>He shook his head in response, reaching up to gently cup San’s face. Yeosang ran his thumbs along the markings on San’s cheeks, the light vanishing beneath. They were warm to the touch, warmer than San’s skin alone, and he leaned up to kiss one of them gently. “Don’t apologize,” he murmured, lips brushing along it. “I am the one who should be sorry, for keeping you hidden and out of sight. You deserve better … not to be kept a secret.”</span>
</p><p>
  <span>“It’s alright, Yeosang. I don’t mind, truly.” San smiled, gently rubbing the Atlantean’s back. “You are a prince, and I am a dragonfish. As long as you are alright, then that’s what matters.”</span>
</p><p>
  <span>“Don’t place so little value on your life, You are more than just a dragonfish to me, San.” Their eyes met, conveying a vast sea of unspoken emotions. “I love you and I will never regret doing so.”</span>
</p><p>
  <span>San’s expression softened. “I love you too, my little starfish.”</span>
</p><p>
  <span>His cheeks grew hot in response. “H-hey, you can’t just say that out of nowhere.”</span>
</p><p>
  <span>“Okay.” The feelers withdrew, settling back into their usual space around San’s throat. “May I … kiss you?”</span>
</p><p>
  <span>“You don’t have to ask for that,” Yeosang murmured. Instead, he leaned up and kissed San himself. Their lips brushed, tender and soft. A hand reached up to thread into the soft strands of his hair, gripping gently and tilting his head back. Yeosang gasped, palms resting flat against the dragonfish’s broad chest as his other hand slipped down the curve of his ass. He began to massage a gentle circle into the area of his tailbone but the kiss didn’t deepen. Instead, San pulled away, but his hands retained their position. </span>
</p><p>
  <span>“I can feel your hardness against my tail. Just a kiss is enough to get you going, hm?”</span>
</p><p>
  <span>Yeosang stared at him for half a moment before the words set in. “D-don’t tease me. It’s purely because I haven’t had any fun for a whole moon phase.”</span>
</p><p>
  <span>“Then allow me to change that.” San’s fingers slipped between his cheeks, pressing lightly against his hole. The Atlantean’s breath caught and San chuckled. He let go of Yeosang’s hair and instead weaseled it between their bodies, seeking out his length. Contrary to human belief, male Atlanteans’ reproductive organs were not the same. They were longer, thinner, with raised ridges and scales along the shaft. Some were highly sensitive, while others had sex strictly for breeding purposes. They didn’t “grow hard” in the traditional sense; they grew longer and softer. Malleable, for easy insertion into whatever hole needed attention—with proper consent of course. </span>
</p><p>
  <span>Yeosang was, unfortunately for him, but delightfully for San, one of the sensitive ones.</span>
</p><p>
  <span>A warm hand fisted his cock, ridges rutting against the dragonfish’s smooth skin and making him involuntarily moan. It felt good, providing him with a much needed touch he had been craving for a long while. Yeosang whimpered weakly as San began to carefully move his hand, using the motion as a distraction to wiggle a finger into his entrance. It didn’t sting, much to his surprise, but San still watched him with careful calculation. The finger pressed deeper and was soon joined by another, stroking along his walls gently. Yeosang wanted to do something, to return the favor, but he felt like nothing more than putty in San’s hands. He always knew how to work him over, how to turn him into a puddle with the barest minimum, but Yeosang never minded. Being taken out of his own mind was something he </span>
  <em>
    <span>needed.</span>
  </em>
</p><p>
  <span>“I’m the luckiest damn creature in the world,” San murmured. His voice was distant despite their closeness. The fingers moving within him pressed deeper, working him open. San’s fingers were longer and thicker, and they reached far more places than Yeosang had ever been able to. </span>
</p><p>
  <span>Luckily San seemed impatient as well. </span>
</p><p>
  <span>He whined weakly as every ministration upon his body stopped. San slipped his fingers free and let go of his length, it pulsating with the need for release. Yeosang trembled against the dragonfish as he was gently turned over and pulled up against his chest. His blurry eyes watched with rapt interest as San reached down to tease at a spot a little bit below where his skin turned to scales. He ran circles around it in quick motion, moaning softly into Yeosang’s ear, before something began to protrude from a slit hidden by pretty black scales. Dragonfish resembled Atlanteans to an extent. They were long but not thin, their lengths spiraled in the same bioluminescent markings as the rest of their bodies. San had been quite the formidable challenge the first time they’d done something like this.</span>
</p><p>
  <span>“You have no idea how badly I want to breed you,” San groaned, lowering Yeosang so he could rub his length in the cleft of the Atlantean’s ass. “I want to make you mine, to start a family with you …” Yeosang groaned but San wasn’t done, his hands trailing up Yeosang’s body to fondle his chest; San squeezed gently. “I want you so badly, Yeosang. I want to be with you forever.” The words carried more weight than one would think. Dragonfish mated for life. They took no other partners, even if their previous mates lost their souls to the water’s surface. It was the ultimate admission.</span>
</p><p>
  <span>“Me too,” he whispered, slotting his hands over San’s. “Even if I have to renounce my place as prince, I don’t care. I want to be with you.” He swallowed, feeling a rush of determination. “What’s a crown if you’re not there to share it with me?”</span>
</p><p>
  <span>“Yeosang …”</span>
</p><p>
  <span>“I want to try,” he continued, “To convince them that you’re not some awful monster. If they don’t listen, then I will leave. My home is with you, not some stony palace. I never wanted to be the prince anyway.”</span>
</p><p>
  <span>San nuzzled into his hair. “You’re sure of this?”</span>
</p><p>
  <span>“Yes, San. I love you,” Yeosang ran his fingers along the arrow-shaped marking on the back of San’s hand. “This is where I belong.”</span>
</p><p>
  <span>San trembled against him. “Then … may I claim you, as a proper dragonfish does?”</span>
</p><p>
  <span>They had spoken about the weight of that implication before, back when they’d first started meeting in secret. It was … scary. Still scary, and probably always would be. But Yeosang was ready; he wanted this. Steeling his nerves, he gave a quick nod.</span>
</p><p>
  <span>“I want that more than anything.”</span>
</p><p>
  <span>“I promise it won’t hurt.”</span>
</p><p>
  <em>
    <span>I trust you,</span>
  </em>
  <span> he thought.</span>
</p><p>
  <span>San’s hands trailed down once more, fingers curling around his length and pressing the tip to Yeosang’s entrance. Giving a wiggle of his hips, he worked the tip inside with little resistance. Yeosang leaned his head back on San’s shoulder as he began to slide deeper, each push splitting him further and further open. By the time he was pressed flush against the scales of San’s tail, he felt like he was being split open from the inside. It burned but it felt oh so good at the same time. Yeosang’s head tipped forward as San began to rub reassuring circles into his hips and he moaned, the noise desperate and wanton.</span>
</p><p>
  <span>His belly glowed faintly, a bulge indicating where San was buried deep within him. That sight alone nearly had his eyes rolling into the back of his skull; he never got tired of it. </span>
</p><p>
  <span>“P-please move,” he gasped, wanting to see the slow slide of that light inside of him.</span>
</p><p>
  <span>San gave in, curling his hands around Yeosang’s thighs and lifting him. He watched with wide-eyed wonder as the combination of light and bulge slowly retreated. Then San let him drop, the light driving home and Yeosang crying out at the sting of pleasure within. His eyes followed the next few thrusts as well, moaning with each push into his body, and then he sank back against San as the dragonfish continued bouncing Yeosang upon him. </span>
</p><p>
  <span>Yeosang whimpered as San leaned over him to awkwardly capture his lips, drinking in every noise and sound that dared escape him. This signaled what was coming, and he whined as he felt the base of San’s shaft begin to grow larger. Normally, this was where they would stop. San would pull away and finish getting Yeosang off with his hand. This time, however, was different.</span>
</p><p>
  <span>San broke the kiss as he pushed Yeosang down a final time. The knot pushed into his entrance and caught there, continuing to swell until it took all of Yeosang’s willpower not to writhe from San’s grip. It didn’t hurt, perse, but it was … intense. Never had he been so full before. San’s knot felt heavy and hot within him, each little shift of his body sending sparks of pleasure rippling through him. Yeosang cried out, throwing his arms behind his head to scrabble weakly at San’s neck. He just needed something to hold onto but he knew—this wasn’t over yet. </span>
</p><p>
  <span>The dragonfish ignored Yeosang’s hands and dropped his face into the Atlantean’s shoulder. His lips dragged along the nape of his neck before San found what he was looking for. It happened so fast Yeosang barely had time to register the pain before the venom of San’s bite leaked into his veins. It was … surprisingly pleasant. It burned but with a pleasant warmth, and Yeosang sagged back against his body with no strength in his limbs at all. His eyes stared blearily at the top of San’s den, mouth open as he just basked in the weird sensations warring in his body. </span>
</p><p>
  <span>San let go of him after a moment, carefully cleaning the bite with his tongue. “Let’s help with this too,” the dragonfish murmured. It was distant and soft, to the point that Yeosang wondered if he fell asleep, but a hand suddenly wrapping around his neglected length proved otherwise. San began jacking him immediately, the sluggish Atlantean only managing a string of garbled noises and tiny cries. It didn’t take long for Yeosang to come, his back arching weakly as he shook and pearlescent bubbles rose and dispersed into the water around them. He watched, head feeling fuzzy, before his eyes trailed down to his stomach once more. The bulge wasn’t any bigger, a bit to his disappointment, but the glow had grown. San’s cum glowed with the same intensity as his markings and Yeosang wasn’t sure why that made him feel so dirty and excited all at once.</span>
</p><p>
  <span>“Did I bite you too hard?” San murmured after a few moments of quiet. </span>
</p><p>
  <span>Yeosang, feeling his mind growing clearer by the minute, shook his head. “No, it actually felt … good.”</span>
</p><p>
  <span>“Ah, I’m glad.” San kissed the place he had bitten, making him shiver. “I had heard we dragonfish could make the bite have no pain at all, but … I’d never done it before.”</span>
</p><p>
  <span>“I promise it didn’t hurt.” He sighed, dreamy. “... I wouldn’t mind if you bit me again in the future. It feels nice to just float here.” Yeosang placed his hand upon his glowing stomach, enjoying the bulging skin at his fingertips. “This too … this is nice.”</span>
</p><p>
  <span>San kissed his neck and then his ear, followed by the side of his head. “As many times as you want. You can have me. Always.”</span>
</p><p>
  <span>They fell into silence again, Yeosang feeling San’s knot begin to go down. They simply basked in each other’s presence until it had grown small enough for San to pull free. Glowing strands followed, drifting away from them and out of the den’s entrance. </span>
</p><p>
  <span>Still, Yeosang felt a nagging feeling pull at his gut. Taking a deep breath, he voiced his concern. “You know I can’t bear children for you, San … is that alright?”</span>
</p><p>
  <span>San turned him over so they were facing each other again, pulling Yeosang close; their noses touched. “I want you for you, Yeosang, not for your ability to raise kids.” He smiled softly. “Besides, we can just adopt a pet dolphin or something. We don’t need little ones. I just need you.”</span>
</p><p>
  <span>His heart squeezed and Yeosang threw his arms around San’s neck, hugging him tightly. “Why are you the most perfect creature in the seven seas?”</span>
</p><p>
  <span>“You’re wrong, Yeosang. You’re the most perfect creature, not me.” San held him tighter. “I love you.”</span>
</p><p>
  <span>“I love you too,” he murmured. For now, he was glad to bask in the afterglow, but he knew tomorrow would be a rush of activity. He still had a kingdom to convince and a mother to appease. Despite the fear of the unknown, Yeosang somehow felt it would be okay. No matter what happened, it would work out. As long as they could remain with each other, it would be worth it.</span>
</p>
  </div><div class="fff_chapter_notes fff_foot_notes"><b>Author's Note:</b><blockquote class="userstuff"><p>find me on twt <a href="https://twitter.com/moonswallowed">@moonswallowed</a> for more spicy content!</p><p>thanks for reading!!</p></blockquote></div></div>
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